‘Moon controls release of methane in Arctic Ocean: Study’

• For thousands of years, the Arctic Ocean has been naturally releasing enormous amounts of methane into the atmosphere—a fact not widely known.
• Methane is a potent greenhouse gas and its release can significantly impact the global climate.
• The world’s oceans are large reservoirs of this gas, where it is stored in the form of solid methane hydrates within the seafloor.
• Climate experts have been warning the world that these leaks can intensify as the ocean warms up.
• This way, we may enter into a self-accelerating loop of more emissions-more warming-more emissions.
• While anthropogenic activities continue to contribute to growing methane concentrations in the atmosphere, the current study indicates that Earth’s sole natural satellite—the Moon—may also be contributing in some form.
• Although ocean methane emissions are considered to be widespread their dynamics and the physical processes behind their evolution are little understood.
• Given the impact of methane as a greenhouse gas, the dynamic of oceanic methane emissions, which could potentially reach the atmosphere, introduces a non-negligible doubt on the global budget of atmospheric methane.

How Arctic Ocean leaks methane?

• In the field of methane emission research today, the Arctic is one of the most important regions worldwide.

• Large quantities of methane are stored in the Arctic in natural gas deposits, permafrost, and as undersea clathrates.
• Methane deposits in permafrost and hydrates are considered to be very sensitive in the expansive shallow-shelf regions, because with the relatively low pressures it would only take a small temperature change to release large amounts of methane.
• The potential for this gas to escape the ocean, and contribute to the greenhouse gas budget in the atmosphere, is an important mystery that scientists are trying to solve.
• The total amount of methane in the atmosphere has increased immensely over the past decades.
• The Arctic is considered ground zero in the debate about the vulnerability of frozen methane deposits – which have been called the “sleeping giants of the carbon cycle” - in the ocean, and if releases were to exceed a tipping point, it could increase the speed of global heating.

There are two potential sources of methane in the Arctic.

• Methyl clathrate: The first source of methane is called methyl clathrate. Methyl clathrates are molecules of methane that are frozen into ice crystals.
  • They can form deep in the Earth or underwater, but it takes very special conditions, with high pressure and low temperature, to make them.
  • If the temperature or pressure changes, the ice that imprisons the methane will break apart, and the methane will escape.
• Presence of organic material: The other major source of methane in the Arctic is the organic matter frozen in permafrost, which contains a lot of carbon.
  • New methane is continuously being produced because the Arctic regions are rich in organic material that is decomposed by microbes in the sediment.
  • The activity of these microbes and thus the biological release rates of methane are also stimulated by increases in temperature.

• The moon controls one of the most formidable forces in nature—the tides that shape our coastlines.
• Tides, in turn, significantly affect the intensity of methane emissions from the Arctic Ocean seafloor.

• Vulnerable to slight pressure change: The gas accumulations, which are in the sediments within a meter from the seafloor, are vulnerable to even slight pressurechanges in the water column.
  • Low tidemeans less of such hydrostatic pressure and higher intensity of methane release.
  • High tide equals high pressureand lower intensity of the release.
• It is the first time that this observation has been made in the Arctic Ocean. It means that slight pressure changes can release significant amounts of methane.

The findings have two major implications.

Methane emission

• The first concerns the amount of methane the Arctic Ocean may be releasing into the atmosphere.
• Methane is an extremely potent greenhouse gas. Once released into the atmosphere, it has 86 times the warming potential of carbon dioxide before it decays to the latter after one or two decades.
• It is currently generated by human activities like fossil fuel production and transportation, livestock agriculture and the decay of organic material in landfills.
• But there is also concernthat, as the planet warms, it could be released by the thawing of frozen gas deposits in the Arctic Ocean known as hydrates.
• Now, the new study provides evidence that Arctic Ocean methane release is occurring more often than previous observation techniques have revealed.

Interaction of global warming with sea level riseto influence Arctic Ocean methane release

• The second implication has to do with how global warming will interact with sea level riseto influence Arctic Ocean methane release.
• While higher temperatures mean greater thawing, the fact that greater water pressure reduces the height and volume of gas releases may mean that sea level rise partly counterbalances the impact of warming.

• The observations were made by placing a tool called a piezometer in the sediments and leaving it there for four days.

• It measured the pressure and temperature of the water inside the pores of the sediment.
• Hourly changes in the measured pressure and temperature revealed the presence of gas close to the seafloor that ascends and descends as the tides change.
• The measurements were made in an area of the Arctic Ocean where no methane release has previously been observed but where massive gas hydrate concentrations have been sampled.
• These observations imply that the quantification of present-day gas emissions in the Arctic may be underestimated.
• High tides, however, seem to influence gas emissions by reducing their height and volume.

Our Earth systems are interconnected in ways that humans are still learning about. And here comes the current study which reveals one of such interconnections in the Arctic: The moon causes tidal forces, the tides generate pressure changes, and bottom currents that in turn shape the seafloor and impact submarine methane emissions.